tee/optee_supplicant: Added optee supplicant

[tkaratapanis]

Summary

This PR introduces to nuttx-apps, the OP-TEE supplicant. Since LIBTEEC already downloads a zip file containing the supplicant and the supplicant requires LIBTEEC, I decided to re-use the downloaded artifact from LIBTEEC and apply the supplicant patch on top of it, in the apps/tee/optee_supplicant/optee_client directory.

The build system will expect CONFIG_OPTEE_SUPPLICANT_VERSION to match CONFIG_LIBTEEC_VERSION otherwise
the build will abort with an error message.

The main reason this application is added, is to provide to OP-TEE secure storage. So an expected (and the currently tested) scenario is to run optee_supplicant as a background app in order to allow Trusted Applications (TAs) running in the OP-TEE to have access to secure files. These files are created on the nuttx side, but all their metadata and contents are only known to OP-TEE since they are encrypted before being "transferred" to nuttx.

To enable the supplicant we need the following:

CONFIG_OPTEE_SUPPLICANT=y
CONFIG_LIBTEEC=y

CONFIG_ALLOW_BSD_COMPONENTS=y
CONFIG_FS_ANONMAP=y
CONFIG_DEV_OPTEE_SMC=y
CONFIG_DEV_OPTEE_SUPPLICANT=y

More info:

• https://github.com/OP-TEE/optee_client
• https://optee.readthedocs.io/en/latest/architecture/secure_storage.html

Impact

No impact to existing users.

Testing

To test the file creation I created 1 nuttx Client Application (CA) and one TA (they are out of scope of this PR and are not included in any way).
The CA invokes the TA by its uuid (145f361e-40f3-11ee-be56-0242ac120002 in this example) and a specific custom function.
In the following scenario the cmd 2 creates a file with some content and then closes the file.
The cmd 3 opens the file by filename and prints the contents (which are the expected).
For this to be possible the optee_supplicant must be running in the background.
The logs follow:

# Run the supplicant in the background, with /data/tee as the filesystem path for OP-TEE
nsh> optee_supplicant -f /data/tee &                                                                                     
optee_supplicant [0:100] 

# Ask OP-TEE to create a secure file, write data to it and then close the file descriptor (cmd 2)
nsh> optee_client 145f361e-40f3-11ee-be56-0242ac120002 2                                                                
I/TA: File created! closing handle!                                                                                                                                                                            
                                                                                                                           
# Ask OP-TEE to open the file and print its contents (cmd 3)
saluki> optee_client 145f361e-40f3-11ee-be56-0242ac120002 3                                                                
I/TA: file found!!                                                                                                         
I/TA: Object content (19 bytes): "Secure OP-TEE data"                                                                                                                          

[cederom]

Thank you @tkaratapanis :-) Please remember to git commit -s (put a signature on the commits, this is mandatory, see https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md).

[tkaratapanis]

Thank you @tkaratapanis :-) Please remember to git commit -s (put a signature on the commits, this is mandatory, see https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md).

I amended my commit with -s :)